1. Field of the Invention
The present invention relates to a power transmission apparatus, and more particularly to an improvement in power transmission apparatus which comprises a front wheel driving device for connecting an output shaft of a power unit to front wheels and a rear wheel driving device for connecting said output shaft to rear wheels.
2. Description of the Prior Art
There has been heretofore known a power transmission apparatus in which a manual clutch is incorporated in a front wheel driving device for obtaining a simultaneous driven state of front and rear wheels and a driven state only of rear wheels which may be suitably alternatively selected by opening and closing the manual clutch (for example, see Japanese Patent Application Laid-Open No. 118,530/84).
In the above-described conventional power transmission apparatus, the switching operation between the simultaneous driven state of front and rear wheels and the driven state only of rear wheels is cumbersome.
The driven state of only rear wheels is required when the vehicle is turned with a small turning radius without allowing the wheels to skid. More specifically, when the vehicle is turned in the simultaneous driven state of front and rear wheels, the turning radius has to be large so as not to impair the synchronism between the front and rear wheel driving devices. Thus, for turning the vehicle with a minimum turning radius without allowing the wheels to skid, the driving of the front wheel has to be stopped for a while.